Starting system for free-piston units



Aprifl 13 1948.

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- smmme SYSTEM FOR FREE PISTON umws 1 Filed Aug. 23, 1944 4 Sheets-Sheet 2 74 70 Il 'l :9 m

STARTING DEVICE FIG. 2 v

INVENTOR April 13, 1948.

K. c. COOPER 2,439,453

STARTING SYSTEM FOR FREE PISTON UNITS Filed Aug. 2:5, 1944 4 Sheet-Sheet 4 2 r SI:

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Patented Apr. 13, 1948 Kenneth C. Cooper, Portland, Conn., assignor to United Aircraft Corporation,

East Hartford,

Conn., a corporation of Delaware Application August 23, 1944, Serial No. 550,875 8 Claims. (Cl. 60-14) This invention relates free-piston units.

The copending application of Meitzler 495,927, filed July 23, 1943, discloses a starting system including an accumulator and a control valve for filling the accumulator and for causing the gas in the accumulator to enter the'air spring of a freepiston unit when the desired pressure in the accumulator is reached. The gas under pressure is manually admitted to the control valve for each starting of the unit. The present invention constitutes an improvement on the disclosure of the copending application by providing for automatically controlling the admission of gas to the control valve.

A feature of this invention isan arrangement for moving the piston or tion prior to the discharge of gas from the accumulator for starting the unit. Another feature is the interconnection of the piston moving structure with the remainder of the starting system so that the gas cannot be discharged from the accumulator until the piston has been placed in starting position.

A feature of this invention is a control system by which, if the unit fails to start on the first attempt, successive attempts will automatically be made until the unit starts or until the starting system is manually shut down.

Free-piston engine-and-compressor units are frequently used in groups as generators of gas under pressure for use, for example, in driving When one or more units is operating, any of the remaining units of the group must be started under load and, therefore, require a higher starting pressure for the gas in the accumulator. A feature of this invention is an automatic control of the discharge pressure in the accumulator dependent upon the discharge pressure against which the unit must be started.

Other objects and advantages will be apparent from the specification and claims, and from the accompanying drawings which illustrate an embodiment of the invention.

Fig. 1 is a sectional view through a free-piston unit incorporating the starting device.

Fig. 2 is a /diagrammatic view of a part of the starting system. r

Fig. 3 is a schematic diagram or the remainder of the starting system.

Fig. 4 is a sectional intake valves. 7

Fig. is a diagrammatic view of the starting system.

The unit shown includes an engine cylinder it view through one of the to automatic starting for pistons into starting posi- A cylinders.

The piston. assemblies are moved apart bythe burning of fuel injected into engine cylinder H! as by a device 32. Air compressed in the air spring cylinders on the power stroke returns the piston assemblies. The assemblies are always maintained at equal distances from the center of the engine cylinder by a linkage, which may include racks. extending from the compressor pistons.

Intake manifold 38 conducts air to intake valves 40, Fig. 4, through which air alternately enters opposite ends of the compressor cylinders. The compressed air leaves the cylinders through discharge valves42, similar to valves and also at opposite ends of the compressor cylinders and passes through scavenge manifold 44 through ports 46 and 48 which are uncovered by pistons 12 and I4 at the end of the power stroke, thereby permitting air to be blown through the engine cylinder and exhaust ports 50 and 52 into exhaust manifold 54.

Starting devices 56 and 58 for the unit are mounted in air spring pistons 28 and 30. The devices are similar and device 58 will be described in detail. Piston '30 forms a housing held within the unit by a threaded ring 60 and having an accumulator chamber 62 in which gas under pressure is collected in readiness for starting. This chamber communicateswith the air spring cylinder through a port 64 closed by a poppet valve 66. The stem 68 of this valve is slidable" in a guide 10 on a cap 12 which closes the end of chamber 62. ment toward the storage chamber and is opened by movement away from the chamber so that pressure of gas within the chamber opens the valve. Pressure of gas in the air spring tends to hold the valve closed during operation of the unit.

Cap I2 has a bore forming a cylinder 14 which receives a piston 16 on the end of valve stem 68. The inner end of cylinder 14 is connected with the storage chamber by one or more ports 18. A coil spring in the cylinder moves the piston toward valve closing position. A head 82 closes he outer end of cylinder 14 and is held in position by stlds 84. extending through both head 82 and cap I Valve 66 closes port 64 by move- A casing 86 on head 82 has a bore 88 in which a plunger 90 is slidable. One end of bore 88 is closed by head 82, the other end by a cover plate 92. Gas under pressure is admitted to the inner end of bore 88 through a channel 94 in casing 86. With plunger 90 in the position shown, gas entering the inner end of the bore is guided into chamber 62 through a channel 96 communicating with a passage 98 in casing 86, cap 82, and head I2, and the head of piston 30 and an intersecting passage 98a in the casing 86.

Passage 98a extends bet-ween and connects passage 98and a parallel passage 99 which communicates with the outer end of cylinder I4. Passage 98a is intersected by bore 88 so that flow of fluid through passage 98a is normally cut oil by plunger 90. This plunger has a groove I00, which, when the plunger is moved to the opposite end of its stroke, permits gas to flow from channel 98 into chann'el 98a and through channel 99 into the outer end of cylinder 14, to cause valve 66 to open.

For moving plunger 90 to the inner end of its stroke, casing 86 has a gas inlet passage I02 which is connected by a groove I03 in plate 92 to the outer end of bore 88. When gas under pressure enters this inlet passage, it moves plunger 90 into a position to close channel 96 and to connect passages 98a and 99 to establish fluid connection between chamber 62 and the outer end of cylinder 14 the outer end of passage 98a being closed by a plug I03a, as shown. When this occurs, the pressures on opposite sides of piston I6 are balanced and the pressure on valve 66 opens the valve for the escape of gas into the air spring.

In starting the unit, gas under pressure is first admitted through channel 94 until a predetermined pressure is built up in chamber 62. After this pressure is reached, gas under pressure is admitted through passage I02 thereby moving plunger 90 to close channel 96 and to cause valve 66 to open. Before this action occurs, the piston assemblies of the unit will have been moved to starting position. The sudden inrush of air into the air springs from chambers 62 in starting devices 56 and 58 will move the piston assemblies rapidly toward each. other.

The starting devices 56 and 58 may be controlled by an automatically operating valve 'I04. which controls the admission of gas under pressure to channel 94 and passage I02. Valve I04 includes a casing I06 having a bore in which a v valve plunger I08 is mounted, the plunger being normally held in the position shown by a spring I I0. The tension of spring IIO may be adjusted by a nut II2 engaging threads in casing I06 to control the pressure in chamber 62 at which the starting device operates.

Casing I06 has an inlet port II4 connected to a source of gas under pressure, and an outlet port II6 connected by a conduit II8 to channel 94. Another outlet port I20 spaced from port H6 is connected by a conduit I22 to passage I02. In the normal position of plunger I08 a groove I24 in the plunger connects ports I I4 and I I6'and another groove I26 establishes fluid connection from port I20 to a chamber I21 at the end of casing I06. When plunger I08 is shifted to the other end of the stroke, as limited bya threaded ring I28, groove I24 connects inlet port II4 with port I20, and another groove I30 connects port II6 to a vent port I32.

For moving plunger I08, the end of easing I06 has a nut I33 with a through passage I34. Nut I33 clamps a bushing I35, the end of which forms against the force of spring I53..

a valve seat engaged by the end of plunger I08. Passage I34 is connected by a branch conduit I36 to conduit I38 which connects with inlet port II4. Branch conduit throttle valve I40 which can provide a restriction greater than any restriction from conduit I38 to chamber 62. When the desired pressure is developed in chamber 62, the pressure in passage I34 acting on the end of plunger I08 moves the plunger against the action of spring IIO to connect port I20 to inlet port II4 for procuring opening of valve 86 .for starting the unit.

A smal1 bleed passage MI in casing I06 provides fluid connection from the end of plunger I90 to groove I30 which connects with vent port I32. This permits gas leaking past the end of plunger I08 to be vented so that the plunger will not be moved from the position shown until the desired pressure has been built up in chamber 62.

A passage I44 in casing 83 connects passage 99 with groove I03 in cap 92 and is closed by a check valve I46. After the starting unit has operated and conduit I22 is vented by plunger I08 returning to the position shown, gas at the right of piston I6 in cylinder I4 may escape past valve I46 so that piston I6 may move into a position for closing poppet valve 66.

The piston assemblies may be automatically moved to the outer ends of their stroke before the starting devices operate. The structure is the same for each piston assembly and only one of the structures will be described. Compressor piston I8 has projecting concentric sleeves I48 and I49, Fig. 3, connected at their outer ends to form a plunger I50 sliding in an annular space I5I between a sleeve I52 and a smaller sleeve I53 mounted within theunit. Only one plunger is shown, but, for purposes of balance, two oppositely placed plungers may be advantageous.

Gas under pressure is admited to the left hand end of space I5I to move the piston assembly of which piston I8 is a part. A valve casing I54 has a sliding plunger valve I56 held in the position shown by a spring I58, In this position gas entering an inlet port I60 passes around a groove I62 in valve I56 to an outlet port I64 connected by a conduit I66 to the end of a bore I68 in a casing I10 at the end of sleeve I52. From bore I68 gas under pressure passes through a channel H2 in casing I10 and one or more channels I14 in head I'I5 on sleeves I52 and I53 to the inner end of space I5I. Gas entering the end of this cylinder moves plunger I50 to the right, carrying with it the attached piston assembly and moving the piston assembly into starting position.

As plunger I50 moves to the right, it uncovers a port I16 connected by a conduit I'I8 to a passage I in a cap I8I in the end of casing I54. Gas entering this passage acts on the end of valve plunger I56 which is in the form Of a valve engaging a seat I82 in a ring I83 at the end of passage I80 and moves the plunger to the left Inlet port I60 is then connected by groove I62 to a port I84 which is connected by conduit I38 to the starting release valve I04.

When valve plunger I56 is moved to the left,'

' port I64 is connected by a groove I86 in plunger I56 to a vent port I08 causing a pressure drop in conduit I66 and permitting a check valve in I90 in bore I68 to be moved by a spring I92 to close passage I'I2.

After the engine is started, plunger as a pump forcing gas under pressure through passages IT4 past a disc valve I94 and through I36 has an adjustable I50 acts the influence of I restriction 231 ing the casing .acts onthe end of-valve plunger I56 to return it to the position shown. While gas under pressure is being admitted to the balance pump, valve I90 is moved into a position to close passage I96. This passage is opened upon return of valve I90 to the normal position shown. During normal operation of the free piston unit, the air pumped by plunger I50 may be delivered through a passage 200 intersecting passage I96 and past a spring loaded check valve I. The check valve 20I is so arranged that it does not open until suil'icient pressure has built up in the chamber surrounding spring I58.

The supply of starting gas to the above described structure may be controlled by a starting cutoff valve. This valve includes a casing 202 having an inlet port 204 connected to a source of gas under pressure and an outlet port 206 connected by a conduit 208 to port I60 of casing I54. Between ports 204 and 206 is a valve 2I0 held against its seat by a spring 2I2 and normally preventing gas from passing between the ports. The valve 2I0 has a stem 2I4, the end of which engages a lever 2I6 on a shaft 2I8. A ro- .iecting arm 220 on lever 2I6 engages the end of a piston 222 in a bore 224 in casing 202. Downward movement of the piston moves the valve stem up to open valve 2l0.

In a bore 226 also in casing 202 is a valve plunger 228 normally held in the position shown by a spring 230 and moved downwardly by gas under pressure entering port 232 to uncover a connecting port 234 between bores 224 and 226. When port 234 is uncovered, pressure entering bore 224 moves the piston down to open valve 2I0 and permit the starting device to operate.

This starting cutoff valve forms the subject matter of a copending application'by Meitzler, Serial No. 550,894, filed August 23, 1944, and is not a part of the present invention. It is suflicientto note for the purpose of the present disclosure, that the fluid pressure applied at port 232 is provided by a stroke indicator so arranged high pressure when the freepiston unit is not operating. This high pressure is suflicient to move plunger 228 and set the starting system in operation immediately whenever the engine stalls.

In operation, with the parts in the position shown, the starting system is set in operation either by pressure entering port 232 or by a manual control lever 236 on shaft 2I8. Withvalve 2I0 open, gas under pressure passes through casfor reducing the rate of pressure build up in this for the starting device to conduit to allow time operate and the gas under pressure is again directed into casing I52 and moves the piston assembly into startingposition for another cycle of operation. The air in the air cushions leaks out slowly as the piston assembly moves. When the unit is started, the starting system may be rendered inoperative by-the cutoif valve. This involves, as described in the above'mentioncd application, Serial No. 550,894, 'a reduction in the pressure at port 232 which permits piston 222 to move upwardly cause valve M0 to be closed.

When the starting system operates on one of a group of units all delivering exhaust gas to a collector, the starting pressure must be high enough to overcome the exhaust pressure. To adjust the starting pressure in chamber 62, a conduit 238, Fig. 2, connects the exhaust manil fold 54 to chamber I21 at the end of plunger I08 in valve I04. The exhaust pressureadded to the pressure of spring IIO increases the pressure required in the starting system before plunger I08 will be shifted to the left to cause the starting system to function.

It is to be understood that the invention is not limited to the specific embodimentherein illustrated and described, but may be used in other ways without departure from its spirit as defined by the following claims.

I-claim: g

1. In a starting system for free-piston units, each unit having at least one piston, and means for moving said piston in one direction into starting position, said starting system including a source of gas under pressure, a valve for admitting gasv from the source to said moving means, means for admitting gas under pressure to the unit for moving the piston in the opposite direction for starting the unit, and means responsive to the position of the piston and operative when the piston reaches for moving said valve to supply gas from said source to said gas-admitting means.

2. In a starting system for free-piston units, each unit having at least one piston, said system includingan accumulator for storing gas under pressure and having a valve for admitting gas from the accumulator to the unit, means controlled by gas under pressure for opening the valve, and a second valve for admitting gas to i the accumulator, said second valve being responing I54 and enters the end of casing I10 to "move the piston assembly, of which piston I8 is a part, into starting position. As the piston assembly reaches starting position and uncovers port I16, gas under pressure passes through conduit I18 and moves valve plunger I56 to the left to connect the gas source to starting release valve I04. Gas is then supplied to the accumulator chamber and when the desired pressure in the chamber is reached, the chamber is opened and discharges gas into the air spring to start the unit.

If the unit fails to start on the first attempt, valve I56 returns to the position shown under spring I58, the space I5I having been connected by conduit I98 to the left hand end of valve. I 56 by the movement of plungsive to pressure changes in said accumulator-and movable when pressure in the accumulator reaches a predetermined value for causing the first valve to open, and means controlled by the position of the piston andoperative only when the piston isin starting position for admitting gas to said second valve only when the piston is in starting position.

3. In a starting system for free-piston units, each unit having at least one piston, said system including an accumulator. for storing gas under pressure and having a valve for admitting gas from the accumulator to the unit, means controlled by gas under pressure for opening the valve, and a second valve for admitting gas to the accumulator, said second valve being responsiye to pressure changes in said accumulator and movable when pressure in the accumulator reaches a predetermined value for cutting off the supply of gas to the accumulator and for causing the first valve to open, and means for cut- I into the position shown to starting position 4. In a starting system for free-piston units, each unit having at least one piston, said system including an accumulator for storing gas under pressure and having a valve for admitting gas from the accumulator to the unit, means controlled by gas under pressure for opening the valve, and a second valvefor admitting gas to the accumulator, said second valve being responsive to pressure changes in said accumulator and movable when pressure in the accumulator reaches a predetermined value for causing the first valve to open, and means responsive to the position of said piston for admitting gas to said second valve only when the piston is in starting position, and means for cutting off the supply of gas to said second valve.

5. In a starting system for a free-piston unit, having at least one piston and a plunger connected to said piston, said system including a source of gas under pressure, means for applying pressure from said source to said plunger to cause the piston to move into starting position, and means controlled by the position of the plunger and automatically operative when the piston reaches starting position for starting the unit, said automatically operative means including an accumulator for gas under pressure, and means responsive to pressure changes in said accumulator and operative when the pressure in the accumulator reaches a, predetermined value for admitting gas to the unit to move the piston.

6. A starting system for a free-piston unit having at least one piston, said system including an accumulator for storing gas under pressure and having a valve for admitting gas from the accumulator to the unit for moving the piston to start the unit, pressure responsive means for causing said valve to open, means for supplying gas to said accumulator, a second valve normally in position to admit gas to the accumulator and movable in response to pressure changes in said accumulator for procuring operation of said pressure responsive means and for cutting ofi said gas supplying means, and a third valve controlled by the position of the piston and operative only when the piston is in starting position for admitting gas to said second valve and thence to the accumulator.

'7. A starting system for a free-piston unit hav- 8 ing at least one piston, said system'including an accumulator for storing gas under pressure and having a valve for admitting gas from the accumulator to the unit for moving the piston to start the unit, pressure responsive means for causing said valve to open, a second valve controlling the supply of gas to said accumulator and movable for simultaneously cutting off the supply of gas to said accumulator and for admitting gas under pressure to said pressure responsive means, pressure actuated means for moving the piston into starting position, and valve means controlled by the position of the piston and movable when the piston is in starting position to admit gas under pressure to said second valve.

8. A starting system for a. free-piston unit having at least one piston,,said systemtincludingan accumulator for storing gas under pressure and having a valve for admitting gasfrom the accumulator to the unit for moving the piston to start the unit, pressure responsive means for causing said valve to open, a second valve controlling the supply of gas to said accumulator and movable for simultaneously cutting of! the supply of gas to said accumulator and for admitting gas under pressure to said pressure responsive means, pressure actuated means for moving the piston into starting position, valve means for admitting gas under pressure to said piston moving means and for controlling the admission of gas to said second valve, and means controlled by the position of the piston and operative when the piston is in starting position to cause said I valve means to move for cutting off the supply of gas "to said piston moving means and for admitting gas under pressure to said second valve.

KENNETH C. COOPER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Pateras Pescara Mar. 14, 1944, 

